Airfoils and the composition of materials from which they are formed are a continuing source of study, examples of which are provided in U.S. Pat. No. 6,709,230 B2 and U.S. Patent Application Publication No. 2004/0043889 A1; each of which is incorporated by reference herein.
With reference to U.S. Pat. No. 6,709,230 B2, there is provided a stationary vane comprising an airfoil structure that, in turn, comprises multiple components such as an outer surface member and a core member bonded together, and whereby each member has a different structural composition. In particular, the outer surface member comprises a body of ceramic matrix composite (hereinafter “CMC”) material, the details and advantages of which are explained therein. The core member comprises a body of monolithic ceramic material as opposed to a composite thereof. As will be understood by one of ordinary skill in the art, a primary difference in the composition of a CMC versus a more monolithic ceramic is that the CMC is constructed with the use of fibers for the purpose of reinforcing the overall strength thereof given use in high load environments. In contrast, a non-composite ceramic is constructed without the inclusion of such fibers.
Airfoils of all designs that are used in gas turbine engines are subjected to a wide range of temperatures and temperature transient conditions. Airfoil designs must be tolerant to stresses induced within the airfoil as a result of such temperatures.